fetchGit: Fix handling of local repo when not using 'master' branch

Add tests checking this behavior.

2 files changed, 31 insertions, 1 deletions

diff --git a/src/libexpr/primops/fetchGit.cc b/src/libexpr/primops/fetchGit.cc
index e92e0638031f..0d0b11958a4b 100644
--- a/src/libexpr/primops/fetchGit.cc
+++ b/src/libexpr/primops/fetchGit.cc
@@ -23,7 +23,7 @@ struct GitInfo
 };
 
 GitInfo exportGit(ref<Store> store, const std::string & uri,
-    std::experimental::optional<std::string> ref, const std::string & rev,
+    std::experimental::optional<std::string> ref, std::string rev,
     const std::string & name)
 {
     if (!ref && rev == "" && hasPrefix(uri, "/") && pathExists(uri + "/.git")) {
@@ -68,6 +68,10 @@ GitInfo exportGit(ref<Store> store, const std::string & uri,
 
             return gitInfo;
         }
+
+        // clean working tree, but no ref or rev specified.  Use 'HEAD'.
+        rev = chomp(runProgram("git", true, { "-C", uri, "rev-parse", "HEAD" }));
+        ref = "HEAD"s;
     }
 
     if (!ref) ref = "master"s;
diff --git a/tests/fetchGit.sh b/tests/fetchGit.sh
index 09e4f742668e..65d673c08854 100644
--- a/tests/fetchGit.sh
+++ b/tests/fetchGit.sh
@@ -93,3 +93,29 @@ git -C $repo add hello
 git -C $repo commit -m 'Bla4'
 rev3=$(git -C $repo rev-parse HEAD)
 nix eval --tarball-ttl 3600 "(builtins.fetchGit { url = $repo; rev = \"$rev3\"; })" >/dev/null
+
+# Update 'path' to reflect latest master
+path=$(nix eval --raw "(builtins.fetchGit file://$repo).outPath")
+
+# Check behavior when non-master branch is used
+git -C $repo checkout $rev2 -b dev
+echo dev > $repo/hello
+
+# File URI uses 'master' unless specified otherwise
+path2=$(nix eval --raw "(builtins.fetchGit file://$repo).outPath")
+[[ $path = $path2 ]]
+
+# Using local path with branch other than 'master' should work when clean or dirty
+path3=$(nix eval --raw "(builtins.fetchGit $repo).outPath")
+# (check dirty-tree handling was used)
+[[ $(nix eval --raw "(builtins.fetchGit $repo).rev") = 0000000000000000000000000000000000000000 ]]
+
+# Committing shouldn't change store path, or switch to using 'master'
+git -C $repo commit -m 'Bla5' -a
+path4=$(nix eval --raw "(builtins.fetchGit $repo).outPath")
+[[ $(cat $path4/hello) = dev ]]
+[[ $path3 = $path4 ]]
+
+# Confirm same as 'dev' branch
+path5=$(nix eval --raw "(builtins.fetchGit { url = $repo; ref = \"dev\"; }).outPath")
+[[ $path3 = $path5 ]]